Anterior osteosynthesis plate for lumbar vertebrae or sacral lumbar vertebra and instrument for positioning same

ABSTRACT

The invention relates to an anterior osteosynthesis plate for lumbar-lumbar or lumbar-sacral vertebrae, the plate being of the type comprising: 
     an elongate body: 
     adapted to cover of the anterior portions of two consecutive vertebrae; 
     possessing an anterior face ( 6 ) and an opposite posterior face ( 7 ); 
     presenting end zones that are interconnected by a connection zone ( 11 ); and 
     provided with two through holes for anchoring screws. 
     According to this invention, the posterior face ( 7 ) of the plate presents a bearing surface ( 12, 13 ), which bearing surface is designed to come into contact with the anterior surface ( 3 ) of the corresponding vertebra, the bearing surfaces ( 12, 13 )being firstly inclined to define an obtuse angle (α) between them in the sagittal plane (S) matching the relative angle between the anterior portions of the two vertebrae, and secondly being interconnected in the connection zone by a concave extension ( 17 ) such that at least the posterior face ( 7 ) of the body presents a profile that is concave in the sadittal plane.

TECHNICAL FIELD

The subject matter of the invention relates to the general technicalfield of intervertebral connection devices for correcting weakening ofthe vertebrae or poor posture of the spinal column by providingstabilization about a longitudinal axis and on the antero-posteriorplane.

More precisely, the subject matter of the invention relates tolumbar-lumbar or lumbar-sacral vertebrae connection devices for fixingto the anterior faces of said vertebrae.

PRIOR ART

Numerous types of intervertebral connection device are known in thestate of the art. Thus, in particular from French design application No.96/7390, an anterior osteosynthesis plate for lumbar vertebrae is knowncomprising an elongate body adapted to cover at least part of theanterior portions of two consecutive vertebrae. The elongate bodypossesses an anterior face and a posterior face opposite thereto forpressing against the anterior faces of the vertebrae. The elongate bodyhas end zones interconnected by a connection zone, and each end zone ishook-shaped. Each end zone is provided with a through hole for a screwthat is to be anchored in a vertebral body.

Such a plate makes it possible to interconnect two vertebrae afterreestablishing the intervertebral space. Such a plate prevents thevertebrae from turning about the longitudinal axis and tilting in theantero-posterior plane, and it enables the vertebrae to be stabilized byencouraging arthrodesis thereof.

The above-described anterior lumbar plate presents a certain number ofdrawbacks. Thus, it appears that each hook-shaped end portion of theplate is for anchoring to the anterior edges of the plates of thevertebral bodies. Unfortunately, it must be understood that from onepatient to another, firstly the anterior edges of the plates are ofvarying profiles, and secondly the size of the intervertebral spacevaries. As a result, it is difficult to position such a plate correctly,even when plates are available in a set of plates having differentdimensions and profiles. In addition to the need to have a wide varietyof plates, it should also be observed that poor positioning of such aplate degrades the quality of intervertebral connection, andconsequently degrades intervertebral stability during bone fusion.

SUMMARY OF THE INVENTION

The object of the invention is to remedy the above-specified drawbacksby proposing an anterior osteosynthesis plate for lumbar-lumbar orlumbar-sacral vertebrae, that is designed to present great adaptabilityduring installation, independently of the dimensions presented by theintervertebral space and of the dimensions and/or profile of thevertebral bodies to which such a plate is to be fixed.

To achieve this object, the invention provides an anteriorosteosynthesis plate for lumbar-lumbar or lumbar-sacral vertebrae, theplate being of the type comprising:

an elongate body:

adapted to cover at least part of the anterior portions of twoconsecutive vertebrae;

possessing an anterior face and an opposite posterior face designed tobe pressed against the anterior faces of the vertebrae;

presenting end zones that are interconnected by a connection zone; and

provided with two through holes for anchoring screws, each formed in arespective one of the end zones.

According to the invention, the posterior face of the body of the platepresents a bearing surface in each end zone, which bearing surface isdesigned to come into contact with the anterior face of thecorresponding vertebra, the bearing surfaces being firstly inclined todefine an obtuse angle between them in the sagittal plane matching therelative angle between the anterior portions of the two vertebrae, andsecondly being interconnected in the connection zone by a concaveextension such that at least the posterior face of the body presents aprofile that is concave in the sagittal plane.

According to another characteristic of the invention, the through holesof the plate are constituted by bores formed in such a manner that theiraxes define respective angles of inclination in the sagittal planerelative to the planes in which the associated bearing surfaces extend,so that said axes diverge from each other going away from the body.

This characteristic makes it possible to obtain screw anchoring indiverging directions suitable for taking up the forces that might act onthe plate.

Various other characteristics appear from the following descriptiongiven with reference to the accompanying drawings which show embodimentsand implementations of the invention as non-limiting examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of an embodiment of an anteriorosteosynthesis plate of the invention mounted on lumbar vertebrae.

FIG. 2 is a three-quarter front view of a plate constituting the firstembodiment as shown in FIG. 1 for lumbar vertebrae.

FIG. 3 is a three-quarter rear view of an anterior plate constitutingthe first embodiment.

FIG. 4 is a front view of a plate constituting the first embodiment.

FIG. 5 is an elevation view in section substantially on line X—X of FIG.4.

FIG. 6 is an elevation view of an instrument enabling a plate of theinvention to be put into place.

FIG. 7 is a plan view of the instrument shown in FIG. 6.

FIG. 8 is a perspective view showing a detail characteristic of theimplementation of the instrument.

FIG. 9 is a diagrammatic view showing a second embodiment of an anteriorplate for making a connection between the sacral and the lumbarvertebrae.

FIG. 10 is a three-quarter front view of a plate constituting the secondembodiment.

FIG. 11 is a three-quarter rear view of a plate constituting the secondembodiment.

FIG. 12 is a front view of a plate constituting the second embodiment.

FIG. 13 is an elevation view in section taken substantially on line X—Xin FIG. 12.

BEST MANNER OF PERFORMING THE INVENTION

FIGS. 1 to 5 show a first embodiment of an anterior osteosynthesis plateI for preventing two lumbar vertebrae from moving relative to eachother, e.g. L₄ and L₅. The plate I of the invention is in the form of anelongate body 2 of substantially parallelepipedal shape possessing alongitudinal axis s lying on a longitudinal plane of symmetry Scoinciding with the sagittal plane of the plate (FIG. 4). The length ofthe body 2 is adapted to cover, at least in part, the anterior faces orportions 3 of the bodies 4 of two consecutive vertebrae, andspecifically L₄ and L₅ in the example shown.

The body 2 has an anterior face 6 and a posterior face 7 opposite fromthe anterior face 6. The posterior face 7 is for pressing against theanterior faces 3 of the vertebral body 4. The body 2 has two end zones 8and 9 interconnected by a central connection zone 11.

In accordance with the invention, in each of its end zones 8 and 9, theposterior face 7 of the body 2 presents a respective bearing surface 12,13 for coming into contact with the anterior face of a vertebra. Eachbearing surface 12, 13 extends in a respective plane P₁, P₂perpendicular to the sagittal plane or plane of symmetry S of the plate2. In FIG. 5, the sagittal plane S is considered as coinciding with theplane of the sheet of paper. According to a characteristic of theinvention, the bearing surfaces 12 and 13 are inclined in the sagittalplane S so as to define between them an obtuse angle α. As can be seenmore clearly in FIG. 5, the planes P₁ and P₂ define between them anobtuse angle α which, in this embodiment, lies in the range 140° to160°, and is preferably about 150°. The value of the obtuse angle αmatches the angle formed between the front portions 3 of the twovertebrae L₄, L₅. In this embodiment, the bearing surfaces P₁, P₂ extendsymmetrically to each other so that the planes P₁, P₂ in which thebearing surfaces extend form a half-angle α with the transverse plane Tperpendicular to the longitudinal axis s.

In a preferred implementation and as can be seen more clearly in FIG. 3,each bearing surface 12, 13 is provided with roughnesses 15 to encourageanchoring between the plate 2 and the anterior portions 3 of thevertebrae. The presence of roughness 15 also facilitates installation ofthe plate 2 on an anterior portion 3 while it is being positionedthereon. In the example shown, the roughnesses 15 are constituted by asuccession of ribs extending in a direction perpendicular to thelongitudinal axis of symmetry s. Naturally, it is clear that theroughnesses 15 could have a variety of profiles other than transverseribs. Also preferably, the grooves begin to be provided at the end edgesof the body 2 and they cover at least part of the area of each of thebearing surfaces 12, 13.

As can be seen more clearly in FIGS. 3 and 5, the bearing surfaces 12,13 are interconnected via the connection zone 11 by means of a concaveextension 17 so that at least the posterior face 7 of the body 2presents a profile that is concave in the sagittal plane S.

According to another preferred characteristic, the plate 2 has throughholes 19 and 20 formed respectively through each of its end zones 8 and9. These through holes 19 and 20 open out in the anterior face 6 and inthe posterior face 7 within the bearing surfaces 12, 13. According to anadvantageous characteristic of the invention, these through holes 19 and20 constitute bores arranged so that their axes a₁, a₂ define respectiveangles of inclination β₁ and β₂ in the sagittal plane S relative to thenormal n to the extension planes P₁, P₂ of the associated bearingsurfaces so that they diverge from each other going away from the body2. In the first embodiment, the angles β₁ and β₂ are identical. Eachbore 19, 20 preferably presents an angle of inclination β₁, β₂ in thesagittal plane that lies in the range 28° to 38°, and is preferablyabout 33°.

The bores 19, 20 serve to pass and position anchoring screws 22 which,when inserted in the bores, are located on the axes a₁ and a₂. Accordingto a preferred characteristic, each bore 19, 20 opens out into theanterior face 6 of the body 2 via a housing 23 for positioning the headof an anchoring screw. Naturally, each housing 23 has an opening ofsection that is suitable for enabling anchoring screws to be insertedfrom the anterior face 6 along the directions defined by the axes a₁ anda₂ of the bores.

According to a preferred characteristic, the body 2 presents in thesagittal plane S and at least on the longitudinal axis of symmetry s,thickness that is substantially constant. In other words, and as can beseen more clearly in FIG. 5, the body 2 has an anterior face 6 whoseprofile is generally concave analogous to the profile of the posteriorface 7. More precisely, in the connection portion 11, the anterior face6 is plane and extends up to the edges of the housings 23. At thehousings 23, the anterior face 6 presents a profile that issubstantially parallel to the bearing surfaces 12, 13. In a preferredembodiment, the anterior face 6 presents over its entire periphery aconvex extension 27 running into the lateral faces 28 of the bodyinterconnecting the anterior and posterior faces 6 and 7. The lateralfaces 28 are preferably interconnected by rounded surfaces. As a result,the body 2 is rounded in shape from its anterior face 6 to its posteriorface 7 without any roughnesses or projecting corners. Such a roundedprofile for the body 2 makes it possible to avoid any risk of lesion orinjury, in particular to the nerves, blood vessels, or tissues locatedin the vicinity.

According to a preferred characteristic, the body 2 presents two notches29 in its opposite lateral faces 28 level with the connection zone 11,which notches are for co-operating with an instrument for positioningthe plate.

By way of example, FIGS. 6 to 8 show an instrument 31 enabling anosteosynthesis plate I of the invention to be positioned. Such aninstrument 31 comprises a handle 32 shaped to present a grip 33extending substantially perpendicularly to the main direction in whichthe handle extends. The end of the handle 32 remote from its end formingthe grip 33 is provided with a guide tube 34 for tools (not shown butknown per se) that perform the various operations involved withanchoring the screws 22. In its lower portion and along a determinedaxial length, the tube 34 is provided with a sighting slot 35 extendingover the front portion of the tube 34 remote from the grip 33 of theinstrument. In its bottom region and diametrically opposite from theslot 35, the tube 34 has a shoe 36 for holding a plate I. As can be seenmore clearly in FIGS. 7 and 8, in the plate-gripping position, theprojection of the longitudinal sighting slot 35 coincides at least inpart with the bottom through section of the guide tube which is to becaused to extend on the same axis as one of the bores 19, 20 of the bodyof the plate I held by the shoe 36. The shoe 36 preferably holds theplate I in position via two studs 38 for engaging by elastic deformationin the notches 29 of the plate I. It should be observed that the plate Iis held in a stable reference position by the shoe 36 insofar as the endopposite from that superposed with the tube 34 bears against the shoe36.

Implementation of an osteosynthesis plate of the invention stemsdirectly from the above description.

Before fitting a plate to the vertebrae of a patient, the portions ofthe anterior faces 3 of the vertebrae that are to receive the bearingsurfaces 12 and 13 are prepared so as to present a flat on eachvertebral body. In order to install the plate I on the vertebrae asprepared in this way, the plate is mounted by being snap-fastened to theguide shoe 36 of the instrument 31. Because of the presence of thelongitudinal slot 35 whose projection coincides with one of the bores19, 20 formed in the plate, the operator can see the conventionaloperations of putting screws 32 into place in the vertebrae. It shouldbe observed that during these operations, the tools are guided indisplacement by the tube 34. In this respect, the relative angle betweenthe guide tube 34 and the gripping shoe 36 is selected so that the axisof the tube 34 coincides with the axis a₁, a₂ with one of the boreswhile the plate 2 occupies its stable position bearing against the shoe.This ensures that the anchoring screws 22 are properly positioned sincethey are well guided by the directed bores 19, 20. It should beconsidered that the presence of the roughnesses 15 which prevents theplate I from slipping make it easier to put the plate I into place.

After one of the anchoring screws 22 has been put into place, theinstrument 31 is separated from the plate 2 merely by applying traction,and after being turned through 180° it is snap-fastened back onto theplate so as to make it possible to perform installing operations on theother anchoring screw 22.

As can be seen from FIG. 1, after assembly, the plate 1 is in contactvia its bearing surfaces 12 and 13 with flats made on the vertebral body4. This provides plane contact between each bearing surface 12, 13 andthe anterior face 3 of the vertebral body 4. The quality of such contactassociated with the anchoring screws 22 being mounted so as to divergemakes it possible to take up forces and stabilize the vertebrae relativeto each other. It should be observed that the connection zone 11 of theplate has a concave extension 17 overlying the intervertebral space. Theclearance left at this location by the plate I allows it to adapt to thevarious shapes of intervertebral space that are to be found.

Susceptibility of Industrial Application

In the embodiment described above, the osteosynthesis plate isparticularly suited for interconnecting two lumbar vertebrae. Naturally,the subject matter of the invention can also be applied to anosteosynthesis plate for installing between a lumbar vertebra and thesacral vertebra, i.e. L₅-S₁. FIGS. 9 to 13 show a second embodiment ofan osteosynthesis plate II of the invention that is suitable forlumbar-sacral vertebrae interconnection.

It should be observed that elements in common between the plate II andthose described for the first embodiment are given the same references.In this second embodiment, the bearing surfaces 12 and 13 of the plateare no longer symmetrical to each other about the transverse axis T. Ascan be seen more clearly in FIG. 13, the two bearing surfaces 12, 13 areinclined relative to each other in the sagittal plane S to define anangle a that matches the angle to be found between the anterior portionsof the two vertebrae L₅-S₁. This obtuse angle α lies in the range 120°and 140°, and is preferably about 130°. In addition, in the sagittalplane, the bore 19 has an angle of inclination β₁ lying in the range 45°to 55°, and preferably about 50°, measured between the normal n to theplane P₁ and the axis a₁ of the bore 19. Similarly, the bore 20 presentsan angle of inclination β₂ in the sagittal plane lying in the range 15°to 25°, and preferably about 20°, taken between the normal n to thebearing surface 12 and the axis a₂ of the bore 20.

The invention is not limited to the embodiments described and shownsince numerous modifications can be made thereto without going beyondthe ambit of the invention.

What is claimed is:
 1. An anterior osteosynthesis plate forlumbar-lumbar or lumbar-sacral vertebrae, the plate being of the typecomprising: an elongated body: adapted to cover at least part of theanterior portions of two consecutive vertebrae; possessing an anteriorface and an opposite posterior face designed to be pressed against theanterior faces of the vertebrae; presenting first and second end zonesthat are interconnected by a connection zone; and provided with twothrough holes for anchoring screws, each formed in a respective one ofthe end zones; wherein the posterior face of the body of the platepresents a first bearing surface in said first end zone, and a secondbearing surface in said second end zone, each bearing surface beingdesigned to come into contact with the anterior face of thecorresponding vertebrae, the bearing surfaces extending on separateplanes and being firstly inclined to define an obtuse angle between saidplanes matching the relative angle between the anterior portions of thetwo vertebrae, and second being interconnected in the connection zone bya concave extension such that at least the posterior face of the bodypresents a profile that is concave in the sagittal plane; and whereineach bearing surface is provided with a roughnesses to encourageanchoring of the plate on the anterior portions of the vertebrae.
 2. Aplate according to claim 1, wherein said through holes have bores formedin such a manner that the bore axes define respective angles ofinclination in the sagittal plane relative to the planes in which theassociated bearing surfaces extend, so that said axes diverge from eachother going away from the body.
 3. A plate according to claim 2, whereinsaid bores each present an angle of inclination in the sagittal planethat is about 33° relative to the normal to the plane in which theassociated bearing surface extends.
 4. A plate according to claim 3,wherein the bearing surfaces extend symmetrically relative to eachother, defining between them an obtuse angle of about 150°.
 5. A plateaccording to claim 2, wherein said bores each present an angle ofinclination in the sagittal plane respectively of about 50° and about20° relative to the normal to the plane in which the associated bearingsurface extends.
 6. A plate according to claim 5, wherein the bearingsurfaces are mutually offset in the sagittal plane by an obtuse angle ofabout 130°.
 7. A plate according to claim 2, wherein each bore opens outin the anterior face of the body via a housing for positioning the headof an anchoring screw.
 8. A plate according to claim 1, wherein the bodyhas two notches in its connection zone for co-operating with aninstrument for positioning the plate.
 9. A plate according to claim 1,wherein the body presents a substantially constant thickness, at leastin the sagittal plane.
 10. A plate according to claim 9, wherein thebody presents a convex extension and rounded lateral faces between theanterior face and the posterior face.
 11. An instrument for positioningan osteosynthesis plate, the instrument comprising a handle providedwith a tool guide tube, the tube being provided at a bottom end of thehandle and in a diametrically opposed manner firsty with a shoe forgripping said plate and secondly with a longitudinal sighting slot witha projection which coincides at least in part with a bottom throughsection of the guide tube, said guide tube being intended to extend onthe same axis as one of a first or second bores of a body of the plate,held by the shoe.